1. Field of the Invention
This invention relates to pneumatic dispensers for compositions in powder or granular form such as, for example, powdered and granular pesticides. More particularly, the invention relates to a hand-held, metering dispenser that will enable the user to carefully control the amount of powder or granules applied at each use site.
2. Description of Related Art
Insects such as ants, crickets and roaches often travel and dwell in areas that are difficult to access, such as the backs of cabinets, and cracks and crevices in wood and concrete structures. A bait product that is deposited in these areas is more effective than baits placed in areas that are well lighted and generally more accessible because such areas are typically frequented by insects only at night.
It is often desired to put a known amount of powder or granule material in hard-to-reach areas. Holes can be drilled in walls, and powder or granule products can then be blown into the walls through the holes. The powder or granule materials can be dispensed by a variety of hand pumps, many using manual or automated pneumatic delivery systems. Liquids can also be pumped into blind areas using many of such devices, but can do serious damage to drywall if over-applied. Also, it is generally known in the trade that a dry granule bit can remain active for a longer period of time than gels or liquids since the moisture tends to break down the stability of the materials.
The use of hand-held pneumatic sprayers for applying liquid or powder pesticides is well known. One such hand-held powder sprayer is disclosed, for example, in U.S. Pat. No. 4,225,065. Such sprayers typically have a chamber or canister that is first loaded with a quantity of the material to be sprayed. The material is then dispensed by manually reciprocating a pneumatic plunger that forces air through the chamber or canister, entraining some of the material to be dispensed and discharging it through an outlet port or spray nozzle. One disadvantage of the known hand-held devices is the difficulty encountered by the user in monitoring the amount of material being applied at each use site. This can be particularly difficult where the sprayer is used to force powder or granules through a small opening into an enclosed structure, such as a wall, or other blind area where the user cannot physically observe the amount of product being dispensed. Although, with the prior art devices, the amount of material dispensed is generally proportional to the number of times the plunger is reciprocated, a device is needed that will enable the user to more reliably monitor the amount dispensed. This is particularly important where the sprayer is used commercially, where the material being sprayed is relatively expensive, and where over-spraying produces no corresponding resultant improvement.
A hand-held powder sprayer is therefore needed that is inexpensive and easy to use, but that preferably includes a simple and reliable, internal metering device that can be used to control the amount of powder being dispensed through the sprayer.
Other prior art pneumatic and aerosol-powered pesticide dusters useful for dispensing powders into wall structures or other blind areas are disclosed, for example, in U.S. Pat. Nos. 4,553,698; 4,648,202; 4,823,505; 5,058,312; 5,309,669 and 5,361,533.
Powder sprayers with pneumatic powder supply systems preferred for use with printing presses are disclosed, for example, in U.S. Pat. Nos. 5,083,710, 5,213,271 and 5,746,131. Powder sprayers using electrostatic charging technology are disclosed, for example, in U.S. Pat. Nos. 4,399,945 and U.S. Pat. No. 4,966,330.
According to a preferred embodiment of the invention, a hand-held, pneumatic metering dispenser is provided that is useful for propelling predetermined quantities of particulate materials such as powder and granules from a canister, through a discharge conduit and toward a target. The apparatus of the invention is particularly useful for spraying known quantities of powdered and granulated pesticide products into walls or other blind structures or locations.
The preferred apparatus of the invention is a hand-held applicator for powder and granules comprising a pneumatic pump, a product canister and a metering scoop insertable into the canister that communicates with a product discharge tube. Once a supply of powder or granular material is loaded into the canister and the metering scoop is installed, a predetermined quantity of the powder or granules is loaded into the scoop simply by rotating the applicator 360xc2x0 around its longitudinal axis. The filled metering scoop is most preferably positioned inside the canister in an upwardly facing position near the top of the cylindrical sidewall. When pressurized air is expelled into the canister from the pneumatic pump, the increased pressure inside the canister forces the predetermined quantity of powder or granular material from the scoop through an orifice disposed in its bottom wall, and into and through the discharge line of the applicator.
The apparatus of the invention can be marketed and used as a new device or as a modification to existing xe2x80x9coff-the-shelfxe2x80x9d sprayers by simply replacing the original discharge assembly. This invention can be also be used in an application where one product is need to be measured and dispensed along with a lighter or heavier weight product, although it is believed that most of the more common applications will involve dispensing a dry product in a stream of air.